The present invention relates to an adaptor assembly for changing the pitch of a contact array of the type employed in a printed circuit board testing apparatus and in other applications.
Automatic printed circuit board testing apparatus are well known in the prior art and usually include a grid or array of contacts which are to be connected with a printed circuit board to be tested. Often, the printed circuit board is interfaced to the grid of contacts using a customizable fixture of the type described in U.S. patent application Ser. No. 179,844 filed Aug. 20, 1980, now abandoned and replaced by U.S. patent application Ser. No. 489,133, filed Apr. 29, 1983, and which corresponds to German laid open Application No. 2,933,862. The grid or array found in a conventional printed circuit board testing apparatus have a pitch of 2.54 mm (0.10 inch) and may have a contact grid of 256 by 256 contacts, thereby providing a total of 65,536 contacts. Typically, selected ones of the 65,536 contacts are connected to predetermined points on the printed circuit board to be tested by the customizable fixture mentioned above.
In the prior art, conventional plastic or fiberglas printed circuit boards have holes drilled therein to receive the conductors of various electronic components to be mounted on the board and with respect to such components, the closest spacing between the individual conductors thereof have typically been on the order or 2.54 mm (0.10 inch). Accordingly, it has been the practice in the prior art with respect to conventional plastic and fiberglas printed circuit boards that the contacts thereon have spacings no closer than 2.54 mm. Consistent with this closest spacing for conventional printed circuit boards, the contact grid or array found in prior art testing apparatuses have typically had a pitch on the order of 2.54 mm. Since the pitch of the contact grid of the testing apparatus has closely coincided with the tightest configuration of contact test points found on printed circuit boards, the pins used in the customizable fixture to interface the board to the grid array did not require undue bending to bring a contact point on the grid into connection with a test point on the printed circuit board.
However, if such a prior art testing apparatus is used with newer designs of printed circuit boards (such as ceramic print circuit boards), which have a much higher contact density, it can be very difficult, if not impossible, to interface the printed circuit board having a high density of contacts to a testing apparatus having a lower density of contacts.
Conventionally, with respect to ceramic printed circuit boards, the contacts thereon can have a pitch as little as 1.27 mm (0.05 inch).
Of course, one solution to this problem would be to redesign the test apparatus and the customizable fixture so that both have a contact grid with a pitch of 1.27 mm. However, this is a rather expensive solution to the problem, since the testing apparatus is expensive. Accordingly, it is an object of the present invention to provide a reducing apparatus for a printed circuit board tester so that the pitch of the contact grid may be simply and inexpensively reduced.